The production of semiconductor devices has employed lithography using a photoresist for microfabrication. The microfabrication is a processing method that includes forming a photoresist thin film on a semiconductor substrate such as a silicon wafer, irradiating the photoresist with active light such as ultraviolet light through a mask pattern with a pattern for a semiconductor device, developing the photoresist, etching the substrate using the obtained photoresist pattern as a protective film, and thus forming minute unevenness corresponding to the pattern on the substrate surface. In recent years, semiconductor devices have been further integrated, and the active light to be used has been changed from a KrF excimer laser (248 nm) to an ArF excimer laser (193 nm) and EUV rays (13.5 nm) having a shorter wavelength. Such a change raises serious issues due to the effect of reflection of active light from the semiconductor substrate.
As an underlayer film between a semiconductor substrate and a photoresist, a film known as a hard mask containing a metallic element such as silicon is used (for example, see Patent Document 1). In this case, the components of the resist are significantly different from those of the hard mask. Therefore, the speeds at which they are removed largely depend on the gas type used in the dry etching. Appropriate selection of the gas type allows the hard mask to be removed by dry etching without largely reducing the film thickness of the photoresist. Thus, in the recent production of semiconductor devices, a resist underlayer film has been arranged between the semiconductor substrate and the photoresist in order to achieve various effects including an anti-reflection effect. A composition for the resist underlayer film has been studied, but there is still a demand for a new material for the resist underlayer film due to a wide variety of characteristics required.
From another viewpoint, a method for modifying the surface of a substrate has been developed. For example, disclosed is a method of using a silane coupling agent having a sulfonyl group to change the surface into a hydrophilic surface after exposure (see Patent Document 2).